Militants who attacked the Ain Amenas gas field in the Sahara had offered to release the hostages in exchange for the freedom of two prominent terror suspects jailed in the United States: Omar Abdel Rahman, a blind sheik convicted of plotting to blow up New York City landmarks and considered the spiritual leader of the 1993 World Trade Center bombing, and Aafia Siddiqui, a Pakistani scientist convicted of shooting at two U.S. soldiers in Afghanistan.

Last week’s desert siege began Wednesday when Mali-based, al-Qaida-linked militants attempted to hijack two buses at the plant, were repelled, and then seized the gas refinery. They said the attack was retaliation for France’s recent military intervention against Islamist rebels in neighboring Mali, but security experts argue it must have taken weeks of planning to hit the remote site.

Algeria says 38 hostages of all nationalities and 29 militants died in the standoff. Five foreign workers remain unaccounted for.

In its announcement Monday, the State Department said at least seven U.S. citizens survived the attack.

Photo: Uncredited / Associated Press

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This undated file image taken from video provided by the SITE Intel Group purports to show terrorist leader Moktar Belmoktar.

This undated file image taken from video provided by the SITE Intel Group purports to show terrorist leader Moktar Belmoktar.

Photo: Uncredited / Associated Press

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Algerian soldiers and officials stand in front of the gas plant in Ain Amenas, seen in background, during a visit organized by the Algerian authorities for news media on Jan 31, 2013.

Algerian soldiers and officials stand in front of the gas plant in Ain Amenas, seen in background, during a visit organized by the Algerian authorities for news media on Jan 31, 2013.

Photo: Associated Press

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Algerian firemen carry a coffin containing the body of a person killed during the gas facility hostage situation at the morgue in Ain Amenas, Algeria.

Algerian firemen carry a coffin containing the body of a person killed during the gas facility hostage situation at the morgue in Ain Amenas, Algeria.

Photo: Anis Belghoul / Associated Press

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An unidentified rescued hostage speaks to the media in a hospital in Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

An unidentified rescued hostage speaks to the media in a hospital in Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

Photo: AP Photo/Canal Algerie via Associated Press TV

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Unidentified rescued hostages pose for the media in Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

Unidentified rescued hostages pose for the media in Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

Photo: AP Photo/Canal Algerie via Associated Press TV

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An unidentified rescued hostage speaks to the media in a hospital Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

An unidentified rescued hostage speaks to the media in a hospital Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

Photo: AP Photo/Canal Algerie via Assiaciated Press TV

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An unidentified rescued hostage receives treatment in a hospital Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

An unidentified rescued hostage receives treatment in a hospital Ain Amenas, Algeria, in this image taken from television Friday Jan. 18, 2013.

Photo: AP Photo/Canal Algerie via Assiaciated Press TV

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An Algerian military truck drives past a road sign indicating the city of Ain Amenas where hostages have been kidnapped by Islamic militants at a gas plant, Friday, Jan. 18, 2013.

An Algerian military truck drives past a road sign indicating the city of Ain Amenas where hostages have been kidnapped by Islamic militants at a gas plant, Friday, Jan. 18, 2013.

Photo: AP Photo/Anis Belghoul

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Abdul Rahman al-Nigeri, a Nigerian fighter reprotedly leading the hostage-taking operation at the BP facility in In Aménas, Algeria.

Abdul Rahman al-Nigeri, a Nigerian fighter reprotedly leading the hostage-taking operation at the BP facility in In Aménas, Algeria.

Military uniforms are displayed for the media after Islamist militants attacked the natural gas plant and took hostages at Ain Amenas, Algeria. The militants were wearing Algerian army uniforms and were equipped with explosives to blow up the plant, according to Algeria’s Prime Minister Abdelmalek Sellal. less

Military uniforms are displayed for the media after Islamist militants attacked the natural gas plant and took hostages at Ain Amenas, Algeria. The militants were wearing Algerian army uniforms and were ... more

Photo: AP Photo

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A truck loaded with empty coffins waits at the main entrance of the hospital where the bodies of persons killed during the hostage situation in a gas plant are gathered in Ain Amenas, Monday, Jan. 21, 2013. At least 81 people have been reported dead, including 32 Islamist militants. less

A truck loaded with empty coffins waits at the main entrance of the hospital where the bodies of persons killed during the hostage situation in a gas plant are gathered in Ain Amenas, Monday, Jan. 21, 2013. At ... more

Photo: AP Photo/Anis Belghoul

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The damaged natural gas plant attacked Islamist militants in Ain Amenas, Algeria. The militants were wearing Algerian army uniforms and were equipped with explosives to blow up the plant, according to Algeria’s Prime Minister Abdelmalek Sellal, who said Monday that at least 81 people died in the four-day operation by government forces to liberate the hostages. less

The damaged natural gas plant attacked Islamist militants in Ain Amenas, Algeria. The militants were wearing Algerian army uniforms and were equipped with explosives to blow up the plant, according to ... more

Photo: AP Photo

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A photo of the Victor Lovelady and his family, posted on the Facebook page of his widow Maureen Lovelady. Victor Lovelady was a Houston engineer killed while being held hostage by militants in an Algeria natural gas facility. The photo shows the couple, along with their two children, Erin and Grant. less

A photo of the Victor Lovelady and his family, posted on the Facebook page of his widow Maureen Lovelady. Victor Lovelady was a Houston engineer killed while being held hostage by militants in an Algeria ... more

Photo: Family photo

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The Amenas natural gas field in the eastern central region of Algeria, where Islamist militants raided and took hostages Wednesday Jan. 16, 2013.

The Amenas natural gas field in the eastern central region of Algeria, where Islamist militants raided and took hostages Wednesday Jan. 16, 2013.

Photo: AP Photo/BP / ASSOCIATED PRESS

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A satellite image provided by DigitalGlobe shows the Amenas Gas Field in Algeria, which is jointly operated by BP and Norway's Statoil and Algeria's Sonatrach.

A satellite image provided by DigitalGlobe shows the Amenas Gas Field in Algeria, which is jointly operated by BP and Norway's Statoil and Algeria's Sonatrach.

Photo: AP Photo/DigitalGlobe

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Statoil's CEO Helge Lund, reacts during a press conference at the centre for relatives to the hostages in Algeria.

Statoil's CEO Helge Lund, reacts during a press conference at the centre for relatives to the hostages in Algeria.

Photo: AP Photo/Hakon Mosvold Larsen/NTB Scanpix

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Defense Secretary Leon Panetta pauses during a news conference in Rome, Wednesday, Jan. 16, 2013. He confirmed on Wednesday that American citizens are among the hostages taken by an Al Qaeda-linked group that seized a gas field in Algeria, calling the action a "terrorist attack, " less

Defense Secretary Leon Panetta pauses during a news conference in Rome, Wednesday, Jan. 16, 2013. He confirmed on Wednesday that American citizens are among the hostages taken by an Al Qaeda-linked group that ... more

Photo: AP Photo/Jacquelyn Martin

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Norway's Prime Minister Jens Stoltenberg checks e-mails on his phone while watching a televised press conference by Statoils CEO Helge Lund at his residence in Oslo on January 17, 2013.

Norway's Prime Minister Jens Stoltenberg checks e-mails on his phone while watching a televised press conference by Statoils CEO Helge Lund at his residence in Oslo on January 17, 2013.

Prime Minister Jens Stoltenberg (R) and Minister Of Foreign Affairs Espen Barth Eide address a press conference on January 17, 2013 in Oslo, Norway to inform about the hostage situation in IN Amenas Algeria.

Prime Minister Jens Stoltenberg (R) and Minister Of Foreign Affairs Espen Barth Eide address a press conference on January 17, 2013 in Oslo, Norway to inform about the hostage situation in IN Amenas Algeria.